用户工具

站点工具

Action disabled: source

learing:examples:string_index_of

String indexOf() and lastIndexOf() Method (查找字符串)

indexOf()可以在字符串里寻找特定字符值的第一个实例。也可以在一个给定的起始端寻找字符。lastIndexOf()同样的是在字符串末尾寻找。

  String stringOne = "<HTML><HEAD><BODY>";
  int firstClosingBracket = stringOne.indexOf('>');

firstClosingBracket等于5,因为第一个>在字符串第五个位置(第一个字符位置为0).也可以用同样的方法想得到第二个>的位置,从firstClosingBracket + 1作为起始端。例如

 stringOne = "<HTML><HEAD><BODY>";
 int secondClosingBracket = stringOne.indexOf('>', firstClosingBracket + 1 );

结果是11,是第二个>的位置

如果想在字符串末尾寻找字符,可以使用lastIndexOf() 这个功能返回最后一个出现的字符位置。

stringOne = “<HTML><HEAD><BODY>”; int lastOpeningBracket = stringOne.lastIndexOf('<');</code>

lastOpeningBracket 等于12,最后一个<的位置。

硬件要求

OCROBOT控制器
USB线

这个例子没有电路图,只需要通过USB线把你的OCROBOT控制器连上电脑,并且打开串口监视器。

代码

/*
  String indexOf() and lastIndexOf() functions
*/
 
void setup() {
  //串口通信
  Serial.begin(9600);
  // 标题:
  Serial.println("\n\nString indexOf() and lastIndexOf()  functions:");
  Serial.println();
}
 
void loop() {
  // indexOf() 返回字符串里的字符位置 
  // 如果你要分析HTML标签,你可以这样
  String stringOne = "<HTML><HEAD><BODY>";
  int firstClosingBracket = stringOne.indexOf('>');
  Serial.println("The index of > in the string " + stringOne + " is " + firstClosingBracket);
 
  stringOne = "<HTML><HEAD><BODY>";
  int secondOpeningBracket = firstClosingBracket + 1;
  int secondClosingBracket = stringOne.indexOf('>', secondOpeningBracket);
  Serial.println("The index of  the second > in the string " + stringOne + " is " + secondClosingBracket);
 
  // 也可以用indexOf() 查找字符串:
  stringOne = "<HTML><HEAD><BODY>";
  int bodyTag = stringOne.indexOf("<BODY>");
  Serial.println("The index of the body tag in the string " + stringOne + " is " + bodyTag);
 
  stringOne = "<UL><LI>item<LI>item<LI>item</UL>";
  int firstListItem = stringOne.indexOf("<LI>");
  int secondListItem = stringOne.indexOf("item", firstListItem + 1);
  Serial.println("The index of the second list item in the string " + stringOne + " is " + secondClosingBracket);
 
  // lastIndexOf() 返回最后一次字符或字符串出现的位置
  int lastOpeningBracket = stringOne.lastIndexOf('<');
  Serial.println("The index of the last < in the string " + stringOne + " is " + lastOpeningBracket);
 
  int lastListItem  = stringOne.lastIndexOf("<LI>");
  Serial.println("The index of the last list item in the string " + stringOne + " is " + lastListItem);
 
 
  // lastIndexOf() 也可以查找字符串:
  stringOne = "<p>Lorem ipsum dolor sit amet</p><p>Ipsem</p><p>Quod</p>";
  int lastParagraph = stringOne.lastIndexOf("<p");
  int secondLastGraf = stringOne.lastIndexOf("<p", lastParagraph - 1);
  Serial.println("The index of the second last paragraph tag " + stringOne + " is " + secondLastGraf);
 
  // 循环:
  while (true);
}
learing/examples/string_index_of.txt · 最后更改: 2023/06/07 04:23 由 127.0.0.1